C TELOPEPTIDE (CTX) TESTING

Code
000.0000
Name
C TELOPEPTIDE (CTX) TESTING
Category
None
Department
Send-Out
Start Date
Expiration Date
Synonyms
CTX, Beta-C-Terminal Telopeptide
CPT Codes
82523
Site
SBMF
Reference Test
23340
ATLAS Test Code

Specimen Information

Type

Gold, SST

Volume

0.5 ml

Transport Info

Centrifuge and immediately transfer serum to separate plastic tube
Frozen

Fasting Required?
True
Patient Instructions

Fasting morning sample recommended since CTx is influenced by food intake and circadian rhythm

Reference Range

Male: up to 0.608 ng/mL
Female: up to 0.534 ng/mL

Methodology

Electrochemiluminescent Immunoassay (ECLIA)

Clinical Significance

CTx and NTx are crosslinked telopeptides of type I collagen that are derived from C-terminal and N-terminal, respectively. Both are efficient markers for bone resorption and have been found to correlate significantly with bone mineral density (BMD) change in the distal third of the radius. These markers differed significantly for groups of patients with fast and slow bone loss while other bone markers did not. This suggests that they are the better markers for assessing the bone metabolic state and thus are the better predictors for the rate of bone loss or fracture risk.

The ß-C-terminal telopeptide (ß-CTx) assay is specific for crosslinked isomerized type I collagen fragments and quantifies all type I collagens. The beta-form is an isomer of C-terminal telopeptide (CTx). ß-CTx, a newer bone marker, has been shown to correlate well with NTx by several studies including an in-house study conducted at SBMF. However, in its favor, ß-CTx can be performed at a significantly lower cost than NTx.

EDTA plasma, or serum, is the sample of choice for testing, rather than a 24-hour urine collection. This judgment is derived not only from the ease of specimen collection and processing, but also from the observation that there is less variation in plasma and serum markers than in urine markers.

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